The present invention relates to an open end wrench capable of fast driving and, more particularly, to an open end wrench capable of fast driving a workpiece without the risk of undesired shifting from the workpiece.
U.S. Pat. No. 1,320,668 discloses a wrench including a stationary jaw and a movable jaw slideable along a guide. The movable jaw is forced against an abutment at an outer end of the guide by a spring bearing against the stationary jaw. An end of the spring is received in a bore in the stationary jaw. The other end of the spring is received in another bore in the movable jaw. An intermediate portion of the spring is exposed between the stationary jaw and the movable jaw. When the user is intended to tighten or loosen a nut, the wrench is turned in a driving direction during which operation the movable jaw remains in contact with the abutment. For reengagement of the wrench with the nut it is necessary only to turn the wrench in the opposite direction, during which operation the movable jaw slides backward against the pressure of the spring and on the edges of the nut. The movable jaw is forced forward again as soon as the bearing surfaces of the stationary and movable jaws are parallel with the sides of the nut. The nut can be tightened or loosened through repeated operations. However, the structural strength of the wrench is insufficient for high-torque operation, as the movable jaw merely encloses the guide and is not enclosed by other members. Furthermore, the guide is irregularly formed in a wrenching space of the wrench, leading to difficulties in processing. Further, the exposed portion of the spring, when compressed by the movable jaw, is liable to bend and, thus, in friction contact with the end edges of the bores of the stationary and movable jaws, leading to non-smooth compression of the spring or even permanent deformation of the spring. Further, the exposed portion of the spring is apt to be contaminated by oil to which debris easily adheres.
U.S. Pat. No. 3,695,125 discloses an open end ratchet wrench including a head having a fixed jaw and an opposed pawl support portion. A pawl and a spring are mounted to an inner side of the pawl support portion. The pawl is biased by the spring and slideable between an extended torquing position and a retracted ratcheting position. Two side caps are fixed to two sides of the head to define a space receiving the pawl and the spring and to prevent disengagement of the pawl and the spring. The pawl includes a stop shoulder to prevent the pawl from moving out of the pawl support portion under the action of the spring. The pawl support portion includes an arcuate section and then extends perpendicularly to the fixed jaw. Such a structure is difficult to process. Furthermore, assembly of the open end ratchet wrench is troublesome. Further, the pawl is merely enclosed at both sides and has insufficient structural strength in the lateral direction. Further, a contact area of the workpiece (such as a nut) engaged with the movable pawl is smaller than a contact area of the workpiece engaged with the fixed jaw. When the nut is tightened to a position adjacent to an object to be fixed, wear or damage to the nut may occur if the nut has insufficient contact area or has a small volume.
U.S. Pat. No. 4,706,528 discloses an adjustable wrench including a fixed jaw and an adjustable jaw. In an embodiment, a sliding jaw portion is provided on the fixed jaw. The sliding jaw includes a rectilinearly extending slot through which a pin is extended, preventing disengagement of the sliding jaw. A plate spring is mounted to an inner face of the fixed jaw to bias the sliding jaw outward. A hole is formed in an end wall of the slot and receives a coil spring to bias the sliding jaw inward. Thus, the sliding jaw is movable inward or outward and can be retained in place under action of the plate spring and the coil spring. Such a wrench is particularly suitable for rotating pipes, but not suitable for tightening or loosening fasteners such as bolts, nuts, or the like. This is because the sliding jaw can only slide rectilinearly, and the shape of the slot will cause the sliding jaw to slide along the slot to a position pressing against the periphery of the pipe.
U.S. Pat. No. 7,024,971 discloses an open end ratchet wrench including first and second stationary jaws. The first stationary jaw supports a movable plate. A space is sandwiched between two face plates of the first stationary jaw to accommodate the movable plate. The movable plate includes two angled slots each receiving a pin extending through the space, avoiding disengagement of the movable plate. The wrench further includes a hole receiving a spring that has an end located outside of the hole for biasing the movable plate. Each angled slot of the movable plate includes a short section and a long section at an angle to the short section such that the movable plate can move in two stages each having a rectilinear travel. However, the stationary jaw is enclosed by the movable plate such that the contact area between the stationary jaw and the workpiece is significantly decreased. Instead, the supporting effect depends on the larger contact area between the workpiece and the movable plate with structural strength weaker than the fixed jaw. The holding force applied by the open end ratchet wrench is reduced.
U.S. Patent Publication No. US 2009/0301271 A1 discloses an open-ended wrench including a first jaw and a second jaw. The second jaw includes an auxiliary jaw retracting opening that receives an auxiliary jaw. A spring is mounted between an end of the auxiliary jaw and an end wall of the auxiliary jaw retracting opening. The auxiliary jaw includes a limiting slot. An auxiliary jaw limiting member extends from a surface of the second jaw through an opening to the auxiliary jaw retracting opening and is coupled with the limiting slot for confining the auxiliary jaw to move between a first position in which the auxiliary jaw is non-longitudinally biased and a second position in which the auxiliary jaw is longitudinally biased. The auxiliary jaw has an arcuate pushing surface and a driving surface. In use, the wrench can drive a nut in a driving direction to a position and then directly move in a reverse direction about the center of the nut. The auxiliary jaw is compressed by a side of the nut and retracts into the auxiliary retracting opening. Thus, the wrench can be directly rotated in the reverse direction through an angle to a next driving position for driving the nut in the driving direction without the need of disengaging from the nut and reengaging with the nut. However, it is difficult to form the auxiliary jaw retracting opening in the second jaw, which is particularly true for axial drilling. Furthermore, the pushing face and the driving surface of the auxiliary jaw must retract into the auxiliary retracting opening so that the wrench can move in the reverse direction to the next driving position. Thus, the widths of the pushing face and the driving surface must be smaller than the size of the auxiliary jaw retracting opening. However, if the nut is of a smaller thickness or if the nut is moved to a position adjacent to a surface of an object to be tightened such that the width of the side of the nut is smaller than the extent of the pushing face and the driving surface, the pushing face and the driving surface may be worn or damaged due to insufficient contact area with the side of the nut.
FIG. 1 shows a reciprocatable open end wrench 50 including a jaw portion 51 having first and second jaws and defining a wrenching space 52. The second jaw includes a concave arcuate surface having a slot. A swing member 53 is received in the slot. A surface of the swing member 53 faces the second jaw and has an arcuate hollow groove for receiving a spring 54. The concave arcuate surface has a curvature corresponds to that of an arcuate face 532 of the swing member 53. The swing member 53 has a clamping face 531 for contacting with a side of a workpiece 90. The clamping face 531 is planar so as to be in surface contact with the side of the workpiece 90 for driving the workpiece 90. An example of such a wrench is disclosed in U.S. Patent Publication No. US 2010/0071516 A1. However, the diameter D53 of the curvature of the arcuate face 532 is not concentric to the wrenching width S between two parallel sides of the workpiece 90. After the wrench 50 has driven the workpiece 90 to rotate in a driving direction, the rotating arc of the diameter D53 can not allow the wrench 50 to rotate in a reverse direction to the next driving direction. Specifically, the wrench 50 has to be moved backwards through a certain travel so that the arcuate face 531 can slide along the side of the workpiece 90 to the next driving position. If the wrench 50 is directly rotated about the center of the workpiece 90 without the backward travel, the arcuate face 531 will be interfered by a side of the workpiece 90. The driving operation provided by the wrench is not smooth.
Thus, a need exists for an open end wrench capable of fast driving of a workpiece without the disadvantages of the above conventional open end wrenches.